1. Field of the Invention
Aspects of the present invention relate to a direct liquid feed fuel cell system, and more particularly, to a direct liquid feed fuel cell system including a high concentration fuel storage unit and a low concentration fuel storage unit.
2. Description of the Related Art
A fuel cell is an electrochemical apparatus that directly transforms chemical energy of a fuel into electrical energy. A direct liquid feed fuel cell generates electricity through an electrochemical reaction between a liquid fuel, such as methanol, and oxygen. A direct liquid feed fuel cell is different from a secondary cell in that the direct liquid feed fuel cell can be operated as long as fuel is supplied from the outside.
A direct liquid feed fuel cell can be directly mounted in a mobile communication device or can be used to charge a rechargeable battery mounted in a mobile communication device.
To use a direct liquid feed fuel cell as a power source of a mobile communication device for a prolonged period of time, low concentration methanol is supplied to an electrode after mixing pure methanol or high concentration methanol with water. Accordingly, the direct liquid feed fuel cell for a mobile communication device requires a high concentration fuel storage. To dilute the high concentration methanol, water is required at the start-up stage of the fuel cell. Thereafter, water to dilute the high concentration methanol is produced by the normal operation of the fuel cell. It takes at least a few minutes to produce enough water in the direct liquid feed fuel cell system through the normal operation to be able to supply low concentration methanol to the electrode. Therefore, at a start-up stage, to minimize the start-up time, the direct liquid feed fuel cell should operate while low concentration methanol is supplied to an electrode diffusion layer. Afterwards, when the direct liquid feed fuel cell operates normally, high concentration methanol may be used as the source of fuel for the fuel cell.
Accordingly, a direct liquid feed fuel cell system having high and low concentration fuel storage units is desirable to supply power to a small mobile communication device.